The invention is based on a system, in particular an electrohydraulic system, for adjusting the contract pressures of a continuously variable gear.
One such system is known from German Patent Disclosure DE 195 19 162 A1, for example, or U.S. Pat. No. 5,971,876. A device for changing the ratio of the gear, having a primary pressure chamber and a secondary pressure chamber, is provided. Moreover, an electrically triggerable primary pressure valve for adjusting the pressure in the primary pressure chamber and an electrically triggerable secondary pressure valve for adjusting the pressure in the secondary pressure chamber are present. The pressure of the primary pressure chamber and the pressure of the secondary pressure chamber can be carried to the secondary pressure valve.
In such a gear, the contract pressures must be adjusted such that no slip of a belt contact means occurs. However, care also be taken to assure that the contract pressures and hence wear not become unnecessarily great. Particularly when the gear is at a standstill, the possibility exists that the contract pressure, generated in the secondary pressure chamber, of the secondary pulley will not be transmitted fully to the primary pulley. An accurate adjustment of the pressure in the primary pressure chamber and of the contract pressure thus generated of the primary pulley is therefore necessary. An accurate adjustment of the pressure in the primary pressure chamber is possible only with difficulty.